content: /**
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
   * compliance with the License. You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software distributed under the License is
   * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
   * the License for the specific language governing permissions and limitations under the License.
   */
  
  package io.reactivex.interop.internal.operators;
  
  import java.util.NoSuchElementException;
  
  import org.reactivestreams.*;
  
  import hu.akarnokd.reactivestreams.extensions.RelaxedSubscriber;
  import io.reactivex.common.*;
  import io.reactivex.flowable.internal.subscriptions.SubscriptionHelper;
  import io.reactivex.observable.*;
  
  public final class SingleFromPublisher<T> extends Single<T> {
  
      final Publisher<? extends T> publisher;
  
      public SingleFromPublisher(Publisher<? extends T> publisher) {
          this.publisher = publisher;
      }
  
      @Override
      protected void subscribeActual(final SingleObserver<? super T> s) {
          publisher.subscribe(new ToSingleObserver<T>(s));
      }
  
      static final class ToSingleObserver<T> implements RelaxedSubscriber<T>, Disposable {
          final SingleObserver<? super T> actual;
  
          Subscription s;
  
          T value;
  
          boolean done;
  
          volatile boolean disposed;
  
          ToSingleObserver(SingleObserver<? super T> actual) {
              this.actual = actual;
          }
  
          @Override
          public void onSubscribe(Subscription s) {
              if (SubscriptionHelper.validate(this.s, s)) {
                  this.s = s;
  
                  actual.onSubscribe(this);
  
                  s.request(Long.MAX_VALUE);
              }
          }
  
          @Override
          public void onNext(T t) {
              if (done) {
                  return;
              }
              if (value != null) {
                  s.cancel();
                  done = true;
                  this.value = null;
                  actual.onError(new IndexOutOfBoundsException("Too many elements in the Publisher"));
              } else {
                  value = t;
              }
          }
  
          @Override
          public void onError(Throwable t) {
              if (done) {
                  RxJavaCommonPlugins.onError(t);
                  return;
              }
              done = true;
              this.value = null;
              actual.onError(t);
          }
  
          @Override
          public void onComplete() {
              if (done) {
                  return;
              }
              done = true;
              T v = this.value;
              this.value = null;
              if (v == null) {
                  actual.onError(new NoSuchElementException("The source Publisher is empty"));
              } else {
                  actual.onSuccess(v);
              }
          }
  
          @Override
          public boolean isDisposed() {
              return disposed;
          }
  
          @Override
          public void dispose() {
              disposed = true;
              s.cancel();
          }
      }
  }
  